Scattering of Neutrons on Fluctuations of the Density of the Thin Films

. The cross section for scattering neutron  on the density of  fluctuations of the  thin films is obtained in the framework of the quantum theory of multiple scattering  in the quasielastic approximation. Inhomogeneity can be caused by dynamic density fluctuations, and be statistical in nature. Fluctuations in the density of the scattering material cause neutron scattering wave. The probability of a collision between a neutron and an atomic nucleus depends on the number of neutrons and on their velocity. The formulas have been obtained under the assumption that the imaginary part of the optical potential is a local operator. It was determined that the scattering in density fluctuations does not contribute to the attenuation of the coherent neutron wave. In the approximation of a thin target the solution of the equation for the total scattering amplitude is identical to the expression obtained in the usual eikonal approximation and differs significantly, at least functionally, from the solution for the case of a thick target. There have been detailed investigations of the reflection and refraction of neutron waves in matter, and the details of their dispersion law have been studied. The results are  hown  also, that  the total cross section for scattering by the complete target becomes universal and does not depend on cross section for scattering by one nucleus. Keywords: 25.40-Ep